docs: def _get_hanging_wall_coeffs_rx(self, C, rup, r_x):
          """
          Returns the hanging wall r-x caling term defined in equation 7 to 12
          """
          # Define coefficients R1 and R2
          r_1 = rup.width * cos(radians(rup.dip))
          r_2 = 62.0 * rup.mag - 350.0
          fhngrx = np.zeros(len(r_x))
          # Case when 0 <= Rx <= R1
          idx = np.logical_and(r_x >= 0., r_x < r_1)
          fhngrx[idx] = self._get_f1rx(C, r_x[idx], r_1)
          # Case when Rx > R1
          idx = r_x >= r_1
          f2rx = self._get_f2rx(C, r_x[idx], r_1, r_2)
          f2rx[f2rx < 0.0] = 0.0
          fhngrx[idx] = f2rx
          return fhngrx